Yup that Shadow Demon. I never quite understood the PA lore despite seeing most of the movies. Was never really a big fan but I really enjoyed the 3rd movie. Reminded me a lot of the original Poltergeist.

Well I was thinking more solo antagonists but yes Kane/The Beast from Poltergeist. I just remembered that now. Good call on Pennywise too. He's probably one of the most powerful. There was also Bagul from Sinister, so I just read but I've never seen that movie.